Displacement compressor with reduced compressor noise

Abstract

A displacement compressor has a housing defining a chamber and having an inlet and an outlet for the chamber. A pair of meshing helical rotors are rotatably supported about parallel axes in the chamber, so that a compressible fluid may be pumped from the inlet to the outlet. A recess in the wall of the housing is positioned in the chamber and around the outlet and has a substantially trapezoidal shape, in plan. The non-parallel edges of the substantially trapezoidal shape are angled with respect to the axial direction of the rotors, preferably by an angle which is substantially equal to the twist angle of the rotors. Noise producing pressure pulsations at the outlet are thereby reduced.

What is claimed as new and desirable to be secured by Letters Patent of the U.S. is: 
     
       1. A displacement compressor comprising: a housing defining a chamber therein and having an inlet and an outlet for the chamber;   a pair of meshing helical rotors rotatably supported about parallel axes in said chamber, whereby a compressible fluid may be pumped from the inlet to the outlet; and   a recess in the wall of said housing, said recess being positioned in the chamber and around the outlet, wherein said recess has a substantially trapezoidal shape, in plan, with non-parallel edges thereof being angled with respect to the axial direction of said rotors,   whereby noise producing pressure pulsations at the outlet are reduced,   wherein each of said non-parallel edges forms an angle with respect to the axial direction of said rotors, said angle being substantially equal to a twist angle of said rotors, and   wherein each of said non-parallel edges of said substantially trapezoidal shape is comprised of a plurality of stepped portions which together approximate a straight line having said angle.